When an electronic equipment is electrically connected to a power line, an antenna, or the like device providing a long signal, it is exposed to transient phase generated by an induction, caused by lightnings or electromagnetic pulses. A gas discharge tube protects the equipment from being damaged by absorbing the energy in the transient phase or by connecting it to ground. Gas discharge tubes are required to be self-recovering, are capable of handling repetitive transients and must function not only without delay but not being too sensitive to cause improper actions in normal operation. These properties should remain unchanged over time, and further, a gas discharge tube should be suitable for mass production with high and uniform quality.
Gas discharge tubes are used for protecting electronic equipment and are also frequently used as switching devices in power switching circuits, for example, in automotive gas-discharge headlights products. Other application are telecommunications and data communications, audio/video equipments, power supplies, welding equipments, electronic igniters for gas heating, architectural securities and military applications and the like.
Early gas discharge tubes included two solid graphite electrodes, separated by a mica layer. A modern conventional gas discharge tube usually includes two end electrodes plus one optionally additional electrode in the form of a center electrode plus one or two hollow cylindrical insulators, made of an electrically insulating material such as a ceramic, a suitable polymer, a glass or the like. As a usual rule, the insulator in a dual-electrode gas discharge tube is soldered to the end electrodes at two sides, joining them hermetically.
For example, the manufacturing process of a gas discharge tube has the following steps: sealing the components of the tube in a light gas at a suitable temperature and at atmospheric pressure in substantial, reducing the external pressure of the tube below atmospheric pressure while simultaneously lowering the temperature to such extent that the heavy gas can not cause diffusions or permeate the tube walls, and the enclosed light gas can diffuse or effuse through the tube walls. Thus it causes a reduction in the total gas pressure inside the tube.
Furthermore, an outside coating of the gas discharge tube has been disclosed, wherein a tin coating is applied to the electrodes, and an annular protective coating is applied to the ceramic insulator. The protective coating is formed from an acid-resistant and a heat-resistant colorant or a varnish which is continuous in the axial direction of the gas discharge tube. In addition, tin-coated leads can be coupled to the electrodes.
Power gas discharge tubes are for protection of electrical equipments against super-voltages and have high current capacity, which spark gap gas discharge tube comprises two carbon electrodes each having a hemispherical configuration and an insulating porcelain housing, whereby the carbon electrodes contains vent holes to the inner thereof to transfer arcs to an inner durable electrode material.
Sum up the above, there's no relevant disclosure of how to make gas discharge tubes inductive.